1. Field of the Invention
The present invention relates to new cement compositions as well as concretes which utilize these cements.
2. Description of the Prior Art
The cements employed at this present time are hydraulic cements which have a base of hydrated compounds of calcium silicate and aluminates of calcium. Amongst these cements, those poorest in lime are the aluminous cements of the "ciment fondu" type and the superaluminous cements such as SECAR 250, SUPER-SECAR, ALCOA CA-25, ASAHI AC.1, etc.. All of these cements nevertheless still assay more than 20% of CaO. Unfortunately in numerous cases lime is a baneful constituent (lowering of the refractory character, solubility in an acid medium, violent dehydration during a fire, and . . . ). Thus it is desirable to have available cements which are free of these disadvantages.
U. S. Pat. No. 3,802,894 describes hydraulic-setting refractory compositions which comprise by weight
(a) 5-8 parts of at least one aluminous hydraulic cement, PA1 (b) 2.5-4 parts of at least one powdery refractory material selected from clay, kaolin, micronized silica, micronized magnesia, micronized chromite and micronized forsterite, PA1 (c) 0.01 to 0.30 parts of at least one dispersing agent selected from the phosphates of alkali metals, the carbonates of alkali metals, the humates of alkali metals, and PA1 (d) 86-92 parts of at least one refractory aggregate. The constituent (b) must have a particle size less than 50 microns, preferably less than 1 micron. The constituents (a), (b) and (c) constitute a cement or binder for the aggregate (d).
U.S. Pat. No. 3,060,043 describes a refractory composition having improved mechanical strength and resistance to abrasion, which comprises by weight 55-90% of a refractory aggregate (chromium ore, calcined alumina, etc.), 9-40% of a cement having a base of calcium aluminate, and 1 to 5% of volatilized silica of a particle size less than 44 microns, with more than half the silica particles being smaller than 10 microns.
The object of the invention is to provide new cements having remarkable properties, as well as concretes which contain these cements as a binders.